1. Technology Field
The present invention generally relates to optical transmitters and receivers. In particular, the present invention relates to an integrated structure for use in optical transmitters and receivers that enables focusing and redirecting of an optical signal to be simply performed.
2. The Related Technology
Optical networking systems, including fiber-optics and optoelectronics, are an important aspect of modem networking circuits for their ability to allow for efficient, accurate, and rapid transmission of data between various components in the network system. As with most communications systems, the efficient use of space in optical networks is of ever-increasing importance. Further, design considerations for such networks must take into account the modularity of the particular components that are included in the network.
Indeed, modular components are desirable in fiber optic systems to reduce the cost of manufacturing the system, which increases the more customized the system becomes. An example of a modular component is an optical transceiver module (“transceiver”). Transceivers usually include an input receiver optical subassembly (“ROSA”) and an output transmitter optical subassembly (“TOSA”). The ROSA includes a photodiode for detecting optical signals and sensing circuitry for converting the optical signals to digital electrical signals compatible with other network components. The TOSA includes a light source, such as a laser, for transmitting optical signals and control circuitry for modulating the laser according to an input digital electrical data signal. The TOSA also includes a lens assembly having an optical lens for focusing the light signals from the laser of the TOSA for receipt by an optical fiber. Additionally, the transceiver includes pluggable receptacles for optically connecting the TOSA and the ROSA with other components within a fiber optic network. The transceiver further includes an electronic connector for mating with a host system, such as a computer or communication device, with which the transceiver operates.
As mentioned, a photodiode and laser are employed in the ROSA and TOSA, respectively, and as such are examples of optoelectronic components. Generally, these optoelectronic components are sensitive electrical devices, and therefore require environmental protection. In response to this need, the photodiode and laser are usually positioned in packaging assemblies within the respective ROSA or TOSA. One such packaging assembly is known as a transistor-outline header or transistor-outline package, referred to herein as a “TO package” or “TO can.” TO packages are widely used in the field of optoelectronics, and may be employed in a variety of applications. As such, the size of TO packages is often standardized, i.e., modular, to facilitate their incorporation into optoelectronic devices, such as ROSAs and TOSAs. TO packages protect the sensitive components contained therein and electrically connect such devices to external components such as printed circuit boards (“PCBs”), which are also located in the transceiver.
With respect to their construction, TO packages often include a cylindrical metallic base with a number of conductive leads extending therethrough in an arrangement that is generally perpendicular to the base. The size of the base and its respective lead configuration is typically designed to fit within one of a variety of standard form factors, such as TO-5 or TO-46 form factors, for instance. The TO package leads are usually hermetically sealed in the base in such a way as to provide mechanical and environmental protection for the components contained in the TO package, and to electrically isolate the leads from metallic portions of the base. Typically, one of the conductive leads is a ground lead that may be electrically connected directly to the base.
Various types of electrical devices are mounted on an interior surface of the TO package base and connected to the leads. Generally, a cover, or cap, is used to enclose this interior surface where such electrical devices are mounted, thereby forming a chamber with the base that helps prevent contamination or device damage.
The particular design of the TO package depends on both the type of optoelectronic device that is mounted on the base and the configuration of the modular component with which the TO package will operate. By way of example, in applications where the optoelectronic device mounted on the base is an optical device such as a laser or photodiode, the cover of the TO package includes a transparent optical window so to allow an optical signal generated or received by the optical device to be transmitted to or from the TO package. These optical TO packages are also known as window cans.
As mentioned, size is of continuing concern in designing ROSAs, TOSAs, and their respective TO packages. Also, as the rates at which data are transmitted in optically related networks increases, it becomes desirable to reduce the spacing between the various components of the ROSA or TOSA. For example, at data rates of 10 gigabits/second, it becomes highly desirable to position certain high speed or RF electronic components relatively closer to the laser and/or photodetector than in previous designs. In doing so, integrity of the data signal in terms of impedance, electromagnetic interference (“EMI”), and crosstalk is preserved. This repositioning may involve moving components inside of the TOSA or ROSA that were previously located outside thereof. It may also involve moving components that were formerly positioned outside the TO package to within the package itself.
Repositioning components relatively closer to the laser and/or photodiode has presented various challenges, especially when such repositioning involves the inclusion of new components within the TO package itself. Commensurate with these challenges is the fact that transceivers and often TO packages have a predefined size that is set according to industry standards. This has therefore necessitated the rearrangement of components traditionally contained within the TO package in order to accommodate the inclusion of new components.
One example of rearranging existing TO package components involves the laser diode of the TO package contained in the TOSA. Previously, the laser diode could be positioned within the TO package so as to project a light beam directly at and through the window included on the cap portion of the package. The light beam could then be focused by the lens assembly before receipt by an optical fiber optically coupled to the TOSA. After the inclusion of additional components, however, the laser diode must often be positioned horizontally and off-center with respect to the window and beam-receiving optical fiber. As such, the laser diode must project its light beam horizontally with respect to its mounting surface. A suitably positioned 45-degree reflector is then typically positioned to deflect the horizontal light beam upward through the window before focusing of the beam by the lens assembly and subsequent receipt by the optical fiber.
The above off-center laser diode configuration, though often necessary, unfortunately adds to the complexity and cost of the TO package both in terms of the number of parts and the number of parameters that must be adjusted for to accurately align the laser diode, reflector, lens/lens assembly, and optical fiber.
As seen by the above discussion, a need exists for optical transmitter and receiver configurations that avoid the above-described challenges. In particular, a need exists for simplifying light beam direction in packages where the laser diode is positioned in an off-center configuration with respect to an optical fiber or other light-carrying component. Additionally, any solution to the above need should reduce the cost and complexity of the device. Any solution should also have applicability to packages including off-center detectors, such as photodiodes.